Each browser-REPL session supports a new top-level "entry" URL that can be used to easily start the REPL in a browser or other JS runtime (i.e. you don't need to have a separate webapp running to initiate the browser-REPL connection)

The entry (and REPL) URLs are available in slots on the browser-REPL's environment, making it trivial to automate browser-REPL sessions with e.g. phantomjs or a headless chromium or etc. This pattern is implemented by a new `exec-env` function; the default is to start the REPL in phantomjs using a temporary script, but it's super-easy to use a regular browser. e.g. this will use Chrome on OS X in the background: